<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <!--
    子标签相对父标签进行定位
    position 和 left right top bottom
    要定位的必要条件:
    父标签的position属性必须改为relative,子标签的属性必须设置为absulte
    然后再结合left right top bottom定位
    -->
   <style>
       body{
           padding: 0;
           margin: 0;
       }

       div{
           background-color: red;
           width: 200px;
           height: 200px;
           margin: 50px;
           position: relative;
       }

       span{
           background-color: green;
           position: relative;
           right: 0;
           bottom: 0;

           /*右下角*/
           right: 0;
           bottom: 0;
       }

   </style>

</head>
<body>
<div>
    <span>213232</span>
</div>
</body>
</html>